Low Pressure Research Articles

Impact of typical environments in China's western mountainous areas on the durability of railway concrete: a review

PurposeThis study aims to analyze the impact mechanism of typical environments in China's western mountainous areas on the durability of railway concrete and propose measures to improve durability.Design/methodology/approachWith the continuous promotion of infrastructure construction, the focus of China's railway construction has gradually shifted to the western region. The four typical environments of large temperature differences, strong winds and dryness, high cold and low air pressure unique to the western mountainous areas of China have adverse effects on the durability of typical railway structure concrete (bridges, ballastless tracks and tunnels). This study identified the characteristics of four typical environments in the western mountainous areas of China through on-site research. The impact mechanism of the four typical environments on the durability of concrete in different structural parts of railways has been explored through theoretical analysis and experimental research; Finally, a strategy for improving the durability of railway concrete suitable for the western mountainous areas of China was proposed.FindingsThe daily temperature difference in the western mountainous areas of China is more than twice that of the plain region, which will lead to significant temperature deformation and stress in the multi-layered structure of railway ballastless tracks. It will result in cracking. The wind speed in the western plateau region is about 2.5 to 3 times that of the plain region, and the average annual rainfall is only 1/5 of that in the plain region. The drying effect on the surface of casting concrete will significantly accelerate its cracking process, leading to serious durability problems. The environmental temperature in the western mountainous areas of China is generally low, and there are more freeze-thaw cycles, which will increase the risk of freeze-thaw damage to railway concrete. The environmental air pressure in the western plateau region is only 60% of that in the plain region. The moisture inside the concrete is more likely to diffuse into the surrounding environment under the pressure difference, resulting in greater water loss and shrinkage deformation of the concrete in the plateau region. The above four issues will collectively lead to the rapid deterioration of concrete durability in the western plateau region. The corresponding durability improvement suggestions from theoretical research, new technology development and standard system was proposed in this paper.Originality/valueThe research can provide the mechanism of durability degradation of railway concrete in the western mountainous areas of China and corresponding improvement strategies.

Deep Neuromuscular Block with Low Pressure Pneumoperitoneum in Laparoscopic Abdominal Surgeries: A Randomized Controlled Trial

Background: Postoperative pain management remains a challenge in laparoscopic abdominal surgeries. Objectives: The purpose of this research was to determine the effects of deep neuromuscular blockade (NMB) in conjunction with low-pressure pneumoperitoneum )PP) on postoperative pain, surgical parameters, and recovery outcomes. Methods: This randomized controlled double-blind study included 44 participants undergoing laparoscopic abdominal surgery. Patients were randomized equally into two groups (22 each): Group D received deep NMB, while group M received moderate NMB using cis-atracurium, through the utilization of computer-generated random numbers enclosed within sealed, opaque envelopes, following a parallel approach. Regarding deep NMB, following an initial dose of 0.15 mg/kg, a continuous infusion of 0.06 - 0.12 mg/kg/hr was administered to maintain a post-tetanic count between 1 and 2, with low PP pressure of 10 - 12 mmHg. Conversely, for moderate NMB, after the same initial dose of 0.15 mg/kg, the continuous infusion commenced upon the train-of-four count returning to 2, with the rate adjusted to sustain a count between 1 and 3, and standard PP pressure of 15 mmHg. The primary outcome was postoperative pain intensity as measured by Numerical Rating Scale (NRS) scores in the post-anesthesia care unit (PACU). The secondary outcomes included postoperative pain intensity measured by NRS scores from 2 hours to 48 hours post-surgery, time to first analgesic administration, cumulative opioid consumption within the initial 48-hour postoperative period, and patient-reported satisfaction with postoperative pain management. Statistical analysis using SPSS v26 included tests for normality (Shapiro-Wilks), with parametric data analyzed by t-test, non-parametric data by Mann-Whitney, and qualitative data by chi-square/Fisher's test. Results: Group D experienced a considerably longer time until the first analgesic rescue compared to group M (9.82 ± 1.5 hours vs. 7.23 ± 1.19 hours, P < 0.001). Morphine consumption in the first 24 hours was lower in Group D (10.77 ± 1.51 mg vs. 13.09 ± 1.74 mg, P < 0.001). At 6, 8, and 12 hours postoperatively, group D exhibited significantly lower pain scores (P < 0.05). Surgical duration, surgical field quality, complication rates, and patient satisfaction were comparable between groups. Conclusions: Deep NMB combined with low-pressure PP provided superior postoperative analgesia without compromising surgical field quality or increasing complications in laparoscopic abdominal surgeries.

Blood trauma in veno-venous extracorporeal membrane oxygenation: low pump pressures and low circuit resistance matter.

Veno-venous extracorporeal membrane oxygenation (VV ECMO) has become standard of care in patients with the most severe forms of acute respiratory distress syndrome. However, hemolysis and bleeding are one of the most frequent side effects, affecting mortality. Despite the widespread use of VV ECMO, current protocols lack detailed, in-vivo data-based recommendations for safe ECMO pump operating conditions. This study aims to comprehensively analyze the impact of VV ECMO pump operating conditions on hemolysis by combining in-silico modeling and clinical data analysis. We combined data from 580 patients treated with VV ECMO in conjunction with numerical predictions of hemolysis using computational fluid dynamics and reduced order modeling of the Rotaflow (Getinge) and DP3 (Xenios) pumps. Blood trauma parameters across 94,779 pump operating points were associated with numerical predictions of shear induced hemolysis. Minimal hemolysis was observed at low pump pressures and low circuit resistance across all flow rates, whereas high pump pressures and circuit resistance consistently precipitated substantial hemolysis, irrespective of flow rate. However, the lower the flow rate, the more pronounced the influence of circuit resistance on hemolysis became. Numerical models validated against clinical data demonstrated a strong association (Spearman's r = 0.8) between simulated and observed hemolysis, irrespective of the pump type. Integrating in-silico predictions with clinical data provided a novel approach in understanding and potentially reducing blood trauma in VV ECMO. This study further demonstrated that a key factor in lowering side effects of ECMO support is the maintenance of low circuit resistance, including oxygenators with the lowest possible resistance, the shortest feasible circuit tubing, and cannulae with an optimal diameter.

Cu/AlN composite and functionally graded materials with high strength and high electrical- and thermal-conductivity fabricated by spark plasma sintering

Abstract In this study, Cu/AlN composites and functionally graded materials (FGMs) were fabricated with the spark plasma sintering (SPS) method. It was observed that a two-step sintering process, involving sintering under low pressure as the initial stage to remove adsorbed chemicals on the powder, was an effective method for producing sintering objects with high relative density. The hardness of the composites significantly increased with higher volume fraction of AlN particles, while electrical- and thermal-conductivity decreased. Nevertheless, the advanse impact of AlN on thermal-conductivity was found to be minimal. Additionally during compression test, a crack was noted at the interface between Cu and Cu-5vol%AlN region in two-layered FGMs after, whereas no such crack was observed in the three-layered FGMs. Therefore, it is confirmed that the concept of FGMs is useful in overcoming the shortcomings of mutually exclusiveness among high strength, high electrical- and high thermal-conductively.

Molecular Simulation of Cyclohexane in Nanoporous Materials: Adsorption of Conformers and Coadsorption with Water and Carbon Dioxide.

Molecular simulation is used to investigate the adsorption of an organic molecule and its different conformers into various nanoporous adsorbents. In more detail, we perform grand canonical Monte Carlo simulations to determine the adsorption isotherms for cyclohexane with its three conformers (chair, boat, and twisted boat) at three different temperatures into a molecular model of active carbons and two metal-organic frameworks (MOFs) (Cu-BTC and Al-Fum). By considering the adsorption of each conformer separately, we show that the adsorption isotherms are weakly dependent on the molecular conformation. When considering the concomitant adsorption of the three conformers under realistic conditions (to verify the population of each conformer in bulk mixtures), we show that the chair conformer is predominantly adsorbed in each material. However, such favorable adsorption mostly reflects the fact that this conformer has the largest population in the bulk mixture under the same thermodynamic conditions. On the contrary, with an increase in the cyclohexane gas pressure, the adsorption of boat and twisted boat conformers increases, while that of the chair conformer decreases as packing (entropy) effects become predominant during confinement. The adsorption of cyclohexane in the active carbon and MOF materials is also considered in the presence of water and CO2 atmospheres. In the case of the Al-fumarate material, the material is found to be strongly organophilic so that water and CO2 adsorption are negligible, and cyclohexane adsorption is not affected by competitive adsorption under any considered thermodynamic condition. On the contrary, for the active carbon and Cu-BTC material, competitive adsorption between cyclohexane and water or CO2 is observed even if cyclohexane adsorption remains preferred. While the different molecules coexist in the adsorbed phase at low pressures, increasing the cyclohexane pressure beyond 103 Pa promotes cyclohexane adsorption concomitantly with water and/or CO2 desorption.

Test and sensitivity analysis of base‐isolated steel frame with low‐friction spherical sliding bearings

AbstractIn Japan, spherical sliding bearings with low friction coefficients are gaining popularity for base‐isolating low‐rise frames that are relatively lightweight. However, the complete dataset of isolators and a base‐isolated frame for evaluating the model sensitivity and response uncertainty are limited. This study first presents the design process, isolation unit‐ and frame‐level testing, and a blind prediction contest conducted on the occasion of full‐scale shaking table testing of a three‐story base‐isolated hospital specimen. The design process utilizes a numerical model that accounts for the velocity and contact pressure dependencies and requires soft‐ and hard‐case simulations with nominal friction coefficients plus and minus standard deviation to consider the uncertainties associated with the bearing behavior. The pre‐shipment isolation unit and frame shake table testing yielded an invaluable dataset for bearings under normal and low contact pressures, low and high velocities, and constant and varying axial loads. The accompanying blind prediction contest provided a valuable dataset for rethinking the impact of modeling uncertainty. In‐depth data analysis and sensitivity analysis were conducted. The sliding coefficient increased under low‐contact pressure and low‐velocity conditions. The static friction coefficient was 1.9 to 4.5 times higher than the dynamic coefficient, but this had little impact on the residual displacement, cumulative travel, and maximum story shear force. The axial force fluctuation, vertical motion, and two‐directional input did not significantly affect the bearing behavior in the test. The test and the following simulations confirmed that the low friction coefficient helped the building contents, that is, medical equipment in this study, remain in order under near‐fault and long‐period ground motions.

Acupuncture as Adjuvant Therapy for Glaucoma: Protocol for a Randomized Controlled Trial.

Glaucoma is a chronic progressive optic neuropathy that necessitates lifelong treatment to reduce the decline of the optic nerve. Due to the extended and continuous treatments required for patients, complementary therapies are often considered alongside conventional treatments to enhance the effectiveness of the treatment. Acupuncture has demonstrated the potential to lower intraocular pressure in previous clinical trials, making it a promising glaucoma intervention. The primary objective of this study is to conduct a single-center randomized control trial involving patients with glaucoma. Acupuncture will be evaluated as an adjunctive therapy. The trial aims to explore its effectiveness for glaucoma. In this single-center randomized controlled trial, participants (N=50) with primary open-angle glaucoma will be randomly assigned to the treatment group, receiving ophthalmic acupuncture with "De Qi" sensation, or the control group, receiving minimum acupuncture stimulation on nonophthalmic acupoints. The intervention will consist of weekly acupuncture treatments for a total of 6 sessions. Participants will be assessed at 8 time points, which are baseline, during the intervention (6 times), and at a 3-month follow-up. The primary outcome measure is a change in the intraocular pressure before and after each acupuncture treatment. Secondary outcomes will include measurements of heart rate and blood pressure before and after acupuncture, best-corrected visual acuity, visual field, optical coherence tomography, optical coherence tomography angiography, the Glaucoma Symptom Scale, and the Glaucoma Quality of Life-15 questionnaire. Recruitment of participants for the trial commenced on June 28, 2023. A total of 10 participants have been enrolled to test the feasibility of the experiment. We anticipate that the preliminary data from this trial will be completed by December 2025. This trial uses rigorous methodology and comprehensive outcome measurements to assess the clinical efficacy of acupuncture as an adjunctive therapy for glaucoma, providing valuable insights for future clinical treatment guidelines. ClinicalTrials.gov NCT05753137; https://clinicaltrials.gov/study/NCT05753137. DERR1-10.2196/57888.

Effects of normal saline versus lactated Ringer's solution on organ function and inflammatory responses to heatstroke in rats.

Heatstroke is a life-threatening condition characterized by severe hyperthermia and multiple organ dysfunction. Both normal saline (NS) and lactated Ringer's solution (LR) are commonly used for cooling and volume resuscitation in heatstroke patients; however, their specific impacts on patient outcomes during heatstroke management are poorly understood. Given that the systemic inflammatory response and multiple-organ damage caused by heat toxicity are the main pathophysiological features of heatstroke, the aim of this study was to evaluate the effects of NS and LR on the production of inflammatory cytokines and the functional and structural integrity of renal and cardiac tissues in a rat model of heatstroke. Fifty-five male Sprague‒Dawley rats were randomly divided into four groups: cold NS or LR infusion postheatstroke (4℃, 4ml/100g, over 10min) and NS or LR infusion without heatstroke induction (control groups). Vital signs, arterial blood gases, inflammatory cytokines, and renal and cardiac function indicators, such as serum creatinine and cTnI, were monitored after treatment. Tissue samples were analysed via HE staining, electron microscopy, and fluorescence staining for apoptosis markers, and protein lysates were used for Western blotting of pyroptosis-related proteins. Compared with LR-treated heatstroke rats, NS-treated heatstroke rats presented lower mean arterial pressures, worsened metabolic acidosis, and higher levels of IL-6 and TNF-α in both the serum and tissue. These rats also presented increased serum creatinine, troponin, catecholamines, and NGAL and reduced renal clearance. Histological and ultrastructural analyses revealed more severe tissue damage in NS-treated rats, with increased apoptosis and increased expression of NLRP3/caspase-1/GSDMD signalling molecules. Similar differences were not observed between the control groups receiving either NS or LR infusion. One NS-treated heatstroke rat died within 24h, whereas all the LR-treated and control rats survived. NS resuscitation in heat-exposed rats significantly promotes metabolic acidosis and the inflammatory response, leading to greater functional and structural organ damage than does LR. These findings underscore the necessity of selecting appropriate resuscitation fluids for heatstroke management to minimize organ damage and improve outcomes.

Low Intraocular Pressure Induces Fibrotic Changes in the Trabecular Meshwork and Schlemm's Canal of Sprague Dawley Rats.

Continuous artificial aqueous humor drainage in the eyes of patients with glaucoma undergoing trabeculectomy likely exerts abnormal shear stress. However, it remains unknown how changes in intraocular pressure (IOP) can affect aqueous humor outflow (AHO). Here, we induced and maintained low intraocular pressure (L-IOP) in healthy Sprague Dawley (SD) rats by puncturing their eyes using a tube (200-µm diameter) for 2 weeks. After the rats were euthanized, their eyes were removed, fixed, embedded, stained, and scanned to analyze the physiological and pathological changes in the trabecular meshwork (TM) and Schlemm's canal (SC). We measured SC parameters using ImageJ software and assessed the expression of various markers related to flow shear stress (KLF4), fibrosis (TGF-β1, TGF-β2, α-SMA, pSmad1/5, pSmad2/3, and fibronectin), cytoskeleton (integrin β1 and F-actin), diastolic function (nitric oxide synthase and endothelial nitric oxide synthase [eNOS]), apoptosis (cleaved caspase-3), and proliferation (Ki-67) using immunofluorescence or immunohistochemistry. L-IOP eyes showed a larger SC area, higher eNOS expression, and lower KLF4 and F-actin expression in the TM and SC (both P < 0.05) than control eyes. The aqueous humor of L-IOP eyes had a higher abundance of fibrotic proteins and apoptotic cells than that of control eyes, with significantly higher TGF-β1, α-SMA, fibronectin, and cleaved caspase-3 expression (all P < 0.05). In conclusion, a persistence of L-IOP for 2 weeks may contribute to fibrosis in the TM and SC and might be detrimental to conventional AHO in SD rat eyes. Clinicians should consider that aberrant shear force induced by aqueous humor fluctuation may damage AHO outflow channel when treating patients.

The Coefficient of Earth Pressure at Rest K0 of Sands up to Very High Stresses

The mechanical behaviour of soils subjected to any stress path in which deviatoric stresses are present is heavily characterised by non-linearity, irreversibility and is strongly dependent on the initial state of stress. The latter, for the majority of geotechnical applications, is normally determined by the at-rest earth pressure coefficient K0, even though this state is valid, strictly speaking, for axisymmetric conditions and for zero-lateral deformations only. Many expressions are available in the literature for the determination of this coefficient for cohesive and granular materials both for normal consolidated and over-consolidated conditions. These relations are available for low to medium stress levels. Results of an extensive experimental investigation on two sands of different mineralogy up to very high stress (120 MPa) are reported in the paper. For reach very high vertical stresses, a special oedometer has been realised. In the loading phase (normal consolidated sands), the coefficient K0n depends on the stress level. It passes from values of about 0.8 to values of about 0.45 in the range of effective vertical stress σ′v = 0.5–4 MPa. Subsequently, K0n is about constant and varies between 0.45 to 0.55 up to very high vertical effective stresses (120 MPa). For the sands employed in the tests, Jaki’s relation did not lead to reliable results at relatively low pressures, while at high pressures, the same relationship seems to lead to reliable predictions if it refers to the constant volume angle of shear strength. For the over-consolidated sands, K0C strongly depends on the OCR, and for very high values of OCR, K0C could be greater than Rankine’s passive coefficient of earth pressure, Kp. This result is due to the very locked structure of the sands caused by the grain crushing, with intergranular contact of sutured and sigmoidal, concavo-convex and inter-penetrating type, that confer to the sand a sort of apparent cohesion and make it similar to weak sandstone.

Study on failure mechanism of cracked coal rock and law of gas migration

China possesses abundant coal resources and has extensive potential for exploitation. Nevertheless, the coal rock exhibits low strength, and the coal seam fractures due to mining activities, leading to an increased rate of gas emission from the coal seam. This poses significant obstacles to the exploration and development of the coal seam. This paper focuses on studying the failure mechanism of fractured coal rock by conducting uniaxial and triaxial compression experiments on the coal rock found at the Wangpo coal mine site. Simultaneously, in conjunction with the findings from the field experiment, a gas migration model of the mining fracture field is constructed to elucidate the pattern of coal seam gas distribution during mining-induced disturbances. The study structure reveals that coal rock exhibits three distinct failure modes: tensile failure, shear failure, and tension-shear failure. The intricate fissure in the rock layer will intensify the unpredictability of rock collapse patterns. The compressive strength of coal rock diminishes as the confining pressure drops. The coal rock in the working face area will collapse as a result of the lack of confining pressure. In the rock strata above the mining fracture zone, the gas pressure is first higher and then significantly falls with time. After 100 days of ventilation, the low gas pressure area changes little, so to ensure the safety of the project, the ventilation time of the fully mechanized mining surface is at least 100 days. The research results will help to establish the core technology system of coal seam development and improve the competitiveness of coal seam resources in China.

Flow-through microfluidic relative permittivity sensor using highly-doped silicon sidewall electrodes

Abstract This paper reports a flow-through sensor for the real-time measurement of the relative permittivity of a flowing fluid. The proposed sensor contains multiple parallel microchannels. Each channel acts as a parallel plate capacitor in which the electrodes are isolated from the fluid. This approach results in a low pressure drop and high sensitivity while the internal volume is only 50 nl. The fabrication technology allows for controllable scaling of the channel geometry. Equally deep microchannels with widths varying between 5 µm and 50 μ m are fabricated. The fabrication technology is compatible with other flow-through sensors, enabling further on-chip integration. The sensor has been characterised using 10 different fluids with relative permittivity values ranging from 1 to 80—including water and water-containing mixtures—at a measurement frequency of 300 kHz. The results show an accuracy within 3% of full scale and the repeated measurements with nitrogen and water show standard deviations of 1.20 and 1.03, respectively.

A novel valve strategy for particulate matter reduction in a gasoline direct injection engine operated at cold conditions

In this study, we proposed a novel intake strategy to reduce Particulate matter (PM) emissions from gasoline direct-injection (GDI) engines during cold-start conditions emissions. This strategy is characterized by generating strong intake turbulence and low in-cylinder pressure during fuel injection through delayed intake valve opening, which theoretically promotes fuel atomization and fuel-air mixture, thereby suppressing PM formation during combustion. Experiments were conducted on a single-cylinder GDI research engine, operating at 1500 rpm, 3, 6, and 8 bar IMEP, and stoichiometric air-fuel ratio conditions with low coolant and lubricant temperatures to experimentally demonstrate the effectiveness of the proposed valve strategy in reducing PM emissions. Benchmark tests were performed using an intake camshaft with intake valve opening (IVO) at −13 °aTDC and intake valve closing (IVC) at 227 °aTDC. The novel strategy uses an intake camshaft with very late IVO at 66 °aTDC and IVC at 226 °aTDC. Two injection pressures (Pinj = 100/200 bar) were used to evaluate the pressure requirement for achieving low PM emissions with both strategies. Start of injection was swept and optimized to match the valve strategy. The results showed that the novel valve strategy leads to a 50%–90% reduction in particle number and mass emissions in cold-start conditions, and a lower injection pressure requirement to achieve comparable particle number and mass emissions compared with the normal one. For the novel valve strategy, the fuel impingement with early injection timings is largely mitigated, and thus an early injection timing shortly before the IVO is recommended.

7668 Rhabdomyolysis Associated with Severe Hypothyroidism

Abstract Disclosure: H. Soe: None. P. Mikkilineni: None. Background: Over 70% of the patients with newly diagnosed hypothyroidism can present with muscle complaints such as weakness, fatigability, cramps, myalgia. However, rhabdomyolysis, which is the rapid breakdown of skeletal muscle cells, is the rare presentation. Clinical Case: A 70-year old male patient with history of rheumatoid arthritis, hyperlipidemia, prior CVA (left hemispheric subcortical stroke) 6 months ago without residual deficit presented to the hospital with poor oral intake and generalized muscle weakness for 3 weeks. He was unable to get out of bed without assistance and also needed adult diapers. Found to have new-onset severe hypothyroidism with TSH 228 uIU/ml (Ref: 0.350-4.940) and FT4 &amp;lt;0.40 ng/dL (Ref: 0.70-1.50), positive TPO antibody 197 IU/ml (Ref: 0-34). No prior thyroid labs were available and no known history of thyroid disorder was recorded. He has never been on Amiodarone or Lithium before. On physical exam, he was alert and oriented. There was no goiter or palpable thyroid nodule. There was no focal neurological deficit and no peripheral edema. There were no other signs and symptoms pertinent to hypothyroidism except mild bradycardia (HR 56-60) and borderline low blood pressure. AM cortisol was 10.1 ug/dL (Ref: 3.7-19.4). EKG showed low-voltage sinus bradycardia. Echocardiogram was normal. Urinalysis was positive for large blood but only 3 RBCs were present which raised the suspicion of rhabdomyolysis. Creatinine kinase (CK) was 15,584 IU/L (Ref: 30-200). Other laboratory studies were significant for acute renal failure with mild hyperkalemia and mild hypocalcemia, also transaminitis; BUN 130 mg/dl (Ref: 8-26), Creatinine 9.51 mg/dl (Ref: 0.72-1.25), eGFR 5 ml/min/1.73 m2 (Ref: &amp;gt;59), AST 435 IU/L (Ref: 5-34), ALT 269 IU/L (Ref: &amp;lt;55), ALP 171 IU/L (Ref: 40-150). On medication review, he was started on Atorvastatin 80 mg daily during prior admission for CVA 6 months ago. He received IV fluids, s/p 1 dose of Hydrocortisone 100 mg IV, Levothyroxine IV 200 mcg, followed by Levothyroxine IV 50 mcg daily x 3 days and switched to Levothyroxine PO 100 mcg daily (weight-based dose). Atorvastatin was on hold. He became anuric during the hospital course and received 2-3 sessions of hemodialysis. 3-4 days later, CK was trending down to 3000 IU/L, FT4 improved to 0.54 ng/dl and there was also significant improvement in kidney and liver functions. The patient was diagnosed with acute renal failure secondary to rhabdomyolysis associated with severe hypothyroidism caused by Hashimoto's thyroiditis, in the setting of high dose statin use. Conclusion: Clinicians should raise the suspicion of rhabdomyolysis in a patient with severe hypothyroidism, especially in patients with recent high dose statin use as rhabdomyolysis can be a rare and fatal complication of severe hypothyroidism, in the presence of precipitating factors. Presentation: 6/2/2024

8204 Rare Asymptomatic Presentation Of A Large Pheochromocytoma

Abstract Disclosure: A. Lorin: None. C.K. Persaud: None. M.H. Kemm: None. Background: Pheochromocytoma is a rare neuroendocrine tumor arising from chromaffin cells of the adrenal medulla. It is associated with excessive release of catecholamines causing symptoms of hypertension, palpitations, diaphoresis, and headaches. These symptoms are particularly prominent with larger pheochromocytomas. We present the case of a large 13 cm pheochromocytoma (PCC) without the typical associated symptoms. Clinical Case: A 45-year-old male with medical history of osteoarthritis and gastroesophageal reflux presented to his primary care doctor with 2 months of intermittent right upper quadrant abdominal pain associated with nausea. Work up with CT abdomen/pelvis found a 9.3 cm heterogeneous right adrenal mass with mass effect on the right liver lobe, superior pole of the right kidney, duodenum, and pancreatic head. Hormonal testing was notable for plasma metanephrine 257.8 pg/mL (0-88), plasma normetanephrine 12063.7 pg/mL (0.0-218.9), 24 hr urine metanephrine 159 mcg/24 hr (58-276), 24 hr urine normetanephrine 22575 mcg/24 hr (156-729), and chromogranin A 5387 mg/mL (0-101.8). Given lab evaluation, diagnosis was made of pheochromocytoma, and patient was initiated on alpha blockade with doxazosin. Patient’s blood pressure and heart rate were at goal prior to doxazosin initiation and patient needed to be decreased from 1 mg daily to 0.5 mg daily due to side effects of low blood pressure and orthostatic hypotension. Patient had an uncomplicated open right adrenalectomy with pathology showing a 13 cm pheochromocytoma with invasion through the capsule into the periadrenal adipose tissue. Genetic testing revealed no known mutation variants associated with PCC. Labs drawn two weeks postoperatively showed resolution of elevated plasma metanephrine, normetanephrine, and chromogranin A. Conclusion: While the patient had an elevated plasma metanephrine, the normetanephrine was predominantly elevated. Such a hormone profile is more common in extra-adrenal PCCs, consistent with cluster 1 associated genes. This noradrenergic phenotype is likely a reason the patient did not have typical symptoms, despite the size of his pheochromocytoma. A proposed pathophysiologic mechanism for this is the dissociation of renal medulla from the cortex given the large size of the tumor. This would lead to lower local availability of corticosteroid to potentiate the conversion of norepinephrine to epinephrine, thus decreasing likelihood of classical PCC symptoms. Despite lack of expected symptoms and an imaging initially concerning for adrenocortical carcinoma, we should recognize the potential for a large adrenal tumor to represent PCC and evaluate accordingly. Presentation: 6/1/2024

7443 Severe Hypothyroidism and Adrenal Insufficiency in a 27-Year-Old Male with Klippel-Feil Syndrome: A Case Report

Abstract Disclosure: S. Almardini: None. F. Haddadin: None. L. Aoun: None. F. Saliba: None. J. Zaidan: None. Background: Klippel-Feil syndrome (KFS) is a rare congenital disorder characterized by improper segmentation of the cervical vertebrae. The classical clinical triad consists of short neck, low posterior hairline, and limited neck mobility. It is uncommonly associated with endocrine abnormalities. We present a rare case of KFS with severe primary hypothyroidism. Case Presentation: A 27-year-old male with KFS presented for evaluation of profound fatigue and lack of energy. His vital signs revealed a heart rate of 50 and a borderline low blood pressure. On physical exam patient was noted to be lethargic and icteric, thyroid exam was limited due to patient short neck. Labs were consistent with severe hypothyroidism TSH of 825 mIU/L, total T4 &amp;lt;0.4 mcg/dL, low 8 AM cortisol of 4.3 mcg/dL, elevated LDL at 333 mg/dL, elevated liver enzymes AST 491 U/L, ALT 294 U/L, neutropenia with WBC 2.69 x10^3/uL 20% neutrophils and anemia Hb 12 g/dL. TPO and thyroglobulin antibodies were positive at 149.0 and 109.0 IU/mL respectively, 21 hydroxylase antibodies were negative. Thyroid Ultrasound showed small and diffusely heterogenous thyroid. Patient was started on Levothyroxine 125 mcg daily and hydrocortisone with improvement in his symptoms as well as normalization of his lipid panel, liver enzymes and neutropenia. The patient was continued on levothyroxine 125 mcg, hydrocortisone was tapered and repeat cortisol levels were normal. Discussion: This case demonstrates an unusual association between KFS and hypothyroidism secondary to Hashimoto thyroiditis, likely representing an incidental finding rather than a causative relationship. The cervical spinal abnormalities and short neck characteristic of KFS could potentially lead to compression of neurological and vascular structures in the neck. However, this is unlikely to fully explain our patient's hypothyroidism. There are few published case reports of KFS with endocrine disorders in the literature that describe incidental findings like autoimmune thyroiditis and hypoparathyroidism, but there is no known biological mechanism linking KFS and endocrine dysfunction. Moreover, there is no evidence in either our patient's case or in existing literature to suggest a higher occurrence of autoimmune disorders like Hashimoto in such individuals. Conclusion: we present a novel case of KFS found incidentally with primary hypothyroidism. While these endocrine disorders could compound the growth delay and developmental issues typically seen in KFS, they do not appear to be causally related. This case highlights the need to monitor endocrine function in KFS patients and serves as a reminder that common conditions may co-occur simply by chance. Presentation: 6/3/2024

8227 Complex Case of Myxedema Coma Complicated by Cardiac Arrest in a Geriatric Patient with Multiple Comorbidities

Abstract Disclosure: M. Parvez: None. L. Makahleh: None. S. Nagpal: None. A. Kavarthapu: None. V. Vedantam: None. Introduction: This case report details a rare instance of cardiac arrest in a patient with myxedema coma, a severe form of hypothyroidism. It highlights the diagnostic and therapeutic challenges in managing such complex endocrine emergencies. Case Presentation: A 70-year-old female with a history of hypothyroidism, type 2 diabetes, atrial fibrillation, pacemaker implantation, and COPD presented with a 3 day history of progressive lethargy and weakness. EMS found her with critically low blood glucose level of 20. History and Examination revealed non-compliance with thyroid medication and myxedematous features including moon-like facies, periorbital edema, generalized edema, elevated JVP, and cold extremities with sluggish capillary refill. In the ER, she was hypotensive, labs showed a significantly elevated TSH level of 30.55 (0.45-4.5), free T3 level of 1.2 (2.3-4.2), free T4 level of 1.12 (0.93-1.70), high lactate, metabolic acidosis, renal impairment, and liver enzyme elevation. These findings, coupled with the clinical presentation, led to the diagnosis of myxedema coma. The patient's critical state was further complicated by distributive shock, shock liver and oliguric AKI. Management included sodium bicarbonate infusion for severe acidosis, IV hydrocortisone, IV levothyroxine, and broad-spectrum antibiotics. Amiodarone was discontinued due to its potential contribution to acute liver injury and hypothyroidism. Despite interventions, she developed acute respiratory failure, requiring intubation and norepinephrine for low mean arterial pressure. Her renal function improved with pressor support, and her lactic acidosis resolved. She recovered quickly and was subsequently extubated. After stabilization, she was switched to oral levothyroxine and discharged. Shortly after discharge, she returned again with generalized weakness, confusion, and dysuria. ER evaluation revealed lethargy, hypotension, hypoglycemia, severe metabolic acidosis, and a UTI. She tested positive for Influenza. While in the ER, she had cardiac arrest, presenting with agonal breathing and PEA. CPR was initiated, achieving ROSC after two rounds and one dose of epinephrine. She was treated again with IV levothyroxine, and IV antibiotics. She recovered well and was discharged to rehab facility with re-education on compliance. Conclusion: This case exemplifies the complexity and challenges in managing a geriatric patient with multiple comorbidities, particularly in the context of myxedema coma. The intricate interplay of endocrine, cardiovascular, respiratory, and infectious complications necessitated a multifaceted and dynamic therapeutic approach. This case underscores the importance of compliance, vigilant monitoring, prompt recognition of complicating factors, and the need for a coordinated multidisciplinary approach in managing similar cases. Presentation: 6/2/2024

Chronic Stress is Allied to Low Blood Pressure: An Unconvincing Truth

Chronic Stress is Allied to Low Blood Pressure: An Unconvincing Truth

7183 Histoplasmosis Of Adrenal In An Immunocompetent Patient From Arizona: A Surprising Biopsy

Abstract Disclosure: R. Habibi: None. S. Penquite: None. N. Ebrahimi: None. R. Cardenas Lara: None. Introduction: Histoplasmosis of adrenal gland in the context of disseminated infection is a rare entity in a non-endemic area. Early diagnosis and treatment can save one’s life. Here we present a case of a patient from Arizona who was referred to us with a large adrenal mass initially resembling malignancy. Presentation: A 58-year-old male with no significant medical history from Bisbee Arizona presented to our clinic with significant weight loss of 120 pounds in 8months, jaundice, fatigue, nausea and vague abdominal pain. He had an abdominal CT scan in a rural area hospital which showed a left adrenal 4.2 x 4.3 x 3.7 cm mass with average HU=40, with interval development from a CT scan 6months prior to that which showed left adrenal 1.5 x 1.3 x 1.3 cm mass. He had the initial CT scan after a mechanical fall. He was experiencing sweating, dizziness and low blood pressure of 90/60 mmhg, but used to have hypertension. Physical examination revealed diffuse jaundice in an ill appearing cachectic individual. Laboratory data were significant for total bilirubin of 4.9, direct bilirubin 0.7. Plasma metanephrines and normetanephrines, 24-hour urine free cortisol, morning cortisol levels and DHEA sulfate were normal. Other findings on the CT scans of head, chest and abdomen were soft tissue thickening between the right posterior 10th and 11th ribs along with hepatosplenomegaly, nodular lung lesions with calcified granuloma, sub centimeter brain lesions within the left putamen/external capsule junction with corresponding mild edema. During the following month after initial visit he developed bilateral tongue masses with dysphagia along with enlarging bilateral adrenal lesions, measuring up to 4.4 cm on the right and 5.2 cm on the left. The patient was admitted to hospital for further extensive work up. He underwent biopsies of left adrenal mass and tongue lesions which demonstrated necrotizing granulomatous inflammation with fungal elements compatible with histoplasmosis. Liposomal amphotericin B was started, which was quickly switched to itraconazole 200mg twice a day once lumbar puncture result was normal. His transient low blood pressures resolved. He was seen in clinic after few weeks with overall improving symptoms. Follow up with imaging of adrenal in few months is planned. He is currently in his third month of treatment for histoplasmosis with itraconazole. Discussion: The presentation of disseminated histoplasmosis can resemble malignancy as illustrated in this case. Southwest of the United States is an unusual geographical area for such infection. Initial unilateral involvement of adrenal as a mass in an immunocompetent individual is also uncommon. Considering dramatic response to antifungal treatment, a clinician should suspect such rare infections when seeing a nonfunctional adrenal mass with rapidly progressive constitutional symptoms. Presentation: 6/3/2024

8191 Navigating The Maze Of Adrenal Insufficiency, A Complex Case Of Late Presentation

Abstract Disclosure: K.N. Pereira: None. V. Sundaram: None. V. Mehta: None. K. Desai: None. B. Agrawal: None. Adrenal insufficiency, a rare but potentially life-threatening endocrine disorder, arises from the inadequate production or ineffective response to adrenal hormones, particularly cortisol and aldosterone. It poses diagnostic challenges, especially in individuals with intricate medical histories and manifests as either primary (Addison's disease) or secondary. The subtlety of initial symptoms often leads to a delayed diagnosis, emphasizing the importance of a high index of suspicion among healthcare providers. Timely recognition and intervention are crucial to prevent adrenal crises, which includes severe hypotension, electrolyte imbalances and life-threatening complications. This case report delves into the presentation, diagnosis, and management of primary adrenal insufficiency in a 51-year-old female with a myriad of co-morbidities who presented with persistent low blood pressure, syncope episodes and dizziness both at rest and with exertion, despite being on midodrine with systolic blood pressure readings ranging from 60s to 80s mmHg. She was also noted to be bradycardic and laboratory results showed hyponatremia, hyperkalemia, hypoglycemia and anemia. She was given prompt fluid resuscitation, stress dose steroids and fludrocortisone, leading to a remarkable improvement in blood pressure and overall clinical status. Subsequent testing showed low serum cortisol level and elevated ACTH level, confirming the diagnosis of primary adrenal insufficiency. Continued steroids resulted in significant symptomatic improvement and with no further episodes of hypotension or syncope on ensuing follow ups. This case serves as a poignant illustration for the need for a heightened clinical suspicion, as the symptoms of adrenal insufficiency can often masquerade within the intricate tapestry of comorbidities. When the utilization of midodrine, aimed at managing orthostatic hypotension, did not abate symptoms, it prompted a thorough investigation into the possibility of underlying adrenal dysfunction. This case also highlights the collaborative, multidisciplinary approach in the management of adrenal insufficiency, with endocrinology playing a pivotal role. Presentation: 6/1/2024